The proposed study deals with the question of how the structure of chondroitin SO4 proteoglycan is controlled by the biosynthetic and catabolic reactions involved in its metabolism by chick embryo chondrocytes. Structural analyses will be carried out to determine whether GalNAc-6-SO4, and GalNAc-4-SO4 residues occur in the same polymer chains in chick embryo chondroitin SO4, and, if so, how these residues are distributed along the hybrid chains. The sequence of intracellular reactions on proteoglycan synthesis will be studied by pulsing monolayers of chondrocytes with labeled precursors and determining the amounts and the structures of the labeled products in the subcellular fractions during a chase period in the presence and absence of NaF, NaCN, puromycin, colchicine, beta-D-xylosides, and other inhibitors of the normal biosynthesis and secretion pathways. Activities observed in these experiments with whole cells will be studied in cell-free systems using both endogenous and exogenous oligosaccharide acceptor substrates. The substrate specificities and the kinetic properties of the beta-glucuronidase and the sulfatases that plays a role in chondroitin SO4 catabolism will be studied using 3H-labeled oligosaccharides prepared from chondroitin-6-SO4 and chondroitin-4-SO4 as substrates.